Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India

Journal of Asian Earth Sciences xxx (2013) xxx–xxx

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Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India Partha Pratim Chakraborty ⇑, Pritam Paul Department of Geology, University of Delhi, Delhi 110007, India

a r t i c l e

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Article history: Available online xxxx Keywords: Palaeoproterozoic Gwalior Alluvial fan Fluvial Palaeoslope Palaeohydraulics

a b s t r a c t The 20 m thick coarse-grained clastic succession in the basal part of Palaeoproterozoic Par Formation, Gwalior Group has been investigated using process-based sedimentology and deductive palaeohydraulics. Bounded between granitic basement at its base and shallow marine succession at the top, the studied stratigraphic interval represents products of an alluvial fan and its strike-wise co-existent braided river system that possibly acted as a tributary for the fan. Detailed facies, facies association analysis allowed identification of two anatomical parts for the fan system viz. proximal and mid fan. While thin proximal fan is represented by products of rock avalanche and hyperconcentrated flows with widely varying rheology, the mid fan is represented by products of sheet floods and flows within streamlets. The interpretation found support from palaeoslope estimation carried out on the fluvial part of the mid fan that plot dominantly within the alluvial fan field demarcated by Blair and McPherson (1994). Dry climatic condition suggested from dominance of stream flow over mass flow deposition within the Par alluvial fan. Strike-wise, the fan is discontinuous and juxtaposed with a braid plain system. In contrast to the fluvial part of fan system, the palaeoslope data from the braid plain system dominantly plot within the ‘natural depositional gap’ defined by Blair and McPherson. A raised palaeoslope for the river systems, as suggested from Proterozoic braid plain deposits around the Globe, is found valid for the Par braid plain system as well. From preponderance of granular and sandy sediments within the alluvial fan and braid plain systems and a pervasive north-westward palaeocurrent pattern within the fluvial systems the present study infers a gently sloping bevelled source area in the south-southeast of the basin with occurrence of steep cliffs only locally. Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction Basin margin sediment cones and aprons are, more often than not, coarse-grained and serve as excellent proxy for tracking past changes in climate, sea/lake level and hinterland tectonics (Gawthorpe and Leeder, 2000; Bose et al., 2008, 2012). Depending on prevailing topography, depositional slope, water discharge pattern and character of sediment load, alluvial fans or braided river systems represent these coarse-grained basin margin wedges (Blair and McPherson, 1994; Chakraborty et al., 2009; Leeder, 2011; Long, 2011). Besides tectonics, climate and hinterland lithology exert significant influence on the volume and grain size of sediments received in such systems. In Precambrian, aggressive weathering in early greenhouse atmosphere (Corcoran et al., 1998; Donaldson and de Kemp, 1998; Eriksson et al., 2001, 2013; ⇑ Corresponding author. E-mail address: [email protected] (P.P. Chakraborty).

Bose et al., 2012) and lack of binding, baffling and trapping of slope sediment by plant roots in absence of land vegetation would have commonly favoured flash flooding and sediment bypass; thereby resulted in more such clastic cones and aprons. Indeed, high availability of sand-size detritus under enhanced Precambrian weathering prompted mass flows and hyperconcentrated flows even in non-fan fluvial environments and often pose great challenge in interpretation of palaeo-environmental setting/s (fan or braided fluvial) of such coarse-grained clastic systems. Debris flows, hyperconcentrated flows and sheet floods triggered by torrential rain also can mislead the interpretation process (Mueller and Corcoran, 1998). More often than not, distinction between the products of alluvial fan and braided fluvial system in rock record remains uncertain in absence of debris flow and sheet flood products (Nemec and Steel, 1988; Harvey, 1990; Reading and Orton, 1991). Addressing the issue, Blair and McPherson (1994) in their seminal paper argued in favour of apparent gap in slope between fans (minimum slope

1367-9120/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jseaes.2013.09.019

Please cite this article in press as: Chakraborty, P.P., Paul, P. Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India. Journal of Asian Earth Sciences (2013), http://dx.doi.org/10.1016/j.jseaes.2013.09.019

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for modern fans 0.026 m/m) and rivers (maximum slope for modern rivers 0.007 m/m) in nature and suggested distinctiveness of alluvial fans in terms of morphology, hydraulic processes, and sedimentological processes and facies assemblages. The follow-up studies (Saito and Oguchi, 2005; Hashimoto et al., 2008; Eriksson et al., 2006, 2008) however, differed with this view and opined in favour of a continuum of slopes between humid region fans and flood plain rivers; the observation of Blair and McPherson (1994) was considered as an artifact of preferential use of data only from arid and semiarid regions (cf. Long, 2011). Notwithstanding possible climatic control on distinctive slope generation that may provoke development of fan and fluvial systems in modern settings, the other important issue is its uniformitarian application in the vegetation-free Precambrian setting. In particular, the 2.00– 1.8 Ga. Palaeoproterozoic time window that has been projected by Van der Neut and Eriksson (1999) as a unique sedimentary palaeo-environmental window when aggressive weathering in extreme and changing climatic condition led to a higher gradient style of sandy braided channel system (Eriksson et al., 2006) and thereby, making the slope controlled palaeohydraulic distinction between the two environments difficult. An unanimous acceptance of this view, however, could not become possible as palaeohydrological data provided by Els (1990), first of its kind, from 3.1– 2.8 Ga Witwatersrand rocks revealed clear separation of slope between fan and fluvial fields. Further, recent studies by Eriksson et al. (2006) and Sarkar et al. (2012) on palaeohydraulics of fluvial systems belonging to different time domains of Proterozoic Eon provided support in favour of steep channel gradients transcending the lower slope bound of fan systems making the claim of Van der

Neut and Eriksson (1999) for unique fluvial style specific to 2.00– 1.80 Ga time slice further weak. In this backdrop, the 20 m thick coarse-grained arenaceous package belonging to the basal part of 1.7–2.0 Ga old Par Formation, Gwalior Group, central India offers a unique opportunity for detailed comparison between field-based facies data and estimated paleo-hydrological parameters so as to reach out to a logical palaeo-environmental modelling (fan or braided river) that can accommodate both lines of evidences. A 25 m thick arenaceous shallow marine succession, deposited initially under tidal action and subsequently by processes related to wave and storm, overlies the studied stratigraphic interval and make up complete profile for the Par succession. Following process-based facies classification, we examined the palaeo-environmental set-up for the concerned stratigraphic interval exposed at three study locations. The paper further considers the facies architectural patterns and hierarchy of surfaces bounding various orders of depositional units within the fluvial association in order to understand controls on sedimentation pattern. 2. Geological setting and age control Unconformably overlying the Archean Bundelkhand Granite– Gneissic Complex (BGGC; Ram Mohan et al., 2012) at its northwestern fringe, the 0.75 km thick undeformed and unmetamorphosed Gwalior Group of sediments (Ramakrishnan and Vaidyanadhan, 2010) preserve a record of pre-Vindhyan sedimentation in central India (Fig. 1). Basement rocks are largely composed of granitoids emplaced within granite–greenstone consisting of ultramafics,

Fig. 1. Geological map of Gwalior basin after Roy et al. (2005) (a). Relative geographic disposition of Gwalior basin with respect to the Bundelkhand craton and the Vindhyan Supergroup of rocks is shown on its left (b) with map of India in the inset. General stratigraphy for the Gwalior Group is given on the right (c) with studied interval marked. The lower half represents the relative disposition of studied sections with their respective GPS locations (d).

Please cite this article in press as: Chakraborty, P.P., Paul, P. Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India. Journal of Asian Earth Sciences (2013), http://dx.doi.org/10.1016/j.jseaes.2013.09.019

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amphibolites, fuchsite quartzites, banded iron-formations (BIF), schists and calc–silicates (Mondal and Zainuddin, 1996; Mondal et al., 2002). The east–west trending basin succession is spread over an exposure area of 1200 sq km area and internally constituted of two Formations viz. Par and Morar, in order of superposition. Whereas the basal Par Formation is arenaceous and represented by conglomerate, coarse-grained granular sandstones and sandstone-shale heterolithics, the overlying Morar Formation is essentially chemogenic represented dominantly by banded iron Formation (BIF) and ferruginous shale with limestones in subordinate volume. A tectono-magmatic event recorded in form of alternated tuff-basalt-limestone sequence demarcates the transition between the two Formations. Towards north and west the Gwalior sediments are concealed under a thick cover of Mesoproterozoic Vindhyans leaving little scope for understanding the original extent of the basin. On the east the boundary of Gwalior basin is demarcated by the northeast–southwest trending fault presently occupied by flowing Sind river. Bedding dips up to 8° all along the exposure stretch suggest no post-depositional tectonic effect. An east–west trending gravity low in the tune of 20 mgal (Verma and Banerjee, 1992) allowed the workers propose a rift-related origin for the basin. However, till date no corroborative signature has been cited from the sediment repository so as to validate the geophysical inference. Indeed, the Gwalior Group of sediments escaped specialised sedimentological attention in terms of processbased facies and palaeo-environmental analyses despite its crucial Paleoproterozoic time frame. Previous studies dealt mainly with general lithological description, lithostratigraphic reconstruction and characterisation of lithodemic units present within the succession (Heron, 1922; Varadarajan and Verma, 1971; Mathur, 1982; Adil, 1999). Although cursory mentions of shallow marine sedimentation under the influence of tide, wave and storm action are available in literature (Absar, 2005; Absar et al., 2009), there is no description for continental sedimentation from the Par Formation. Absar et al. (2009) suggested severe weathering in the provenance of Gwalior sediments from geochemical signatures of clastic Par succession e.g. strong depletion of mobile elements, strong positive correlation between Al2O3 and TiO2 and high Plagioclase Index of Alteration (PIA) values. Depositional age for the Gwalior lithopackage is constrained on the basis of dates obtained from mafic lavas present within the basin or within its basement. The available dates are based mostly on non-robust Rb–Sr or40Ar/39Ar systematics. The emplacement ages of two phases of dykes within the basement of Gwalior basin i.e. within the Bundelkhand Granite Massif are dated as of 2150 and 2000 Ma through 40Ar/39Ar systematics (Mallikharjuna Rao et al., 2005). Rb–Sr dating of mafic rocks present within the basin has yielded dates of 1830 ± 200 Ma (Crawford, 1970; Crawford and Compston, 1971). Taking into consideration the radiometric ages of basement mafic dykes and recalculating the Rb-Sr dates from the intrabasinal mafics, Absar et al. (2009) bracketed the Gwalior depositional history between 2000 and 1791 Ma. Such time frame coincides well with the time window within which a unique steepsloping braided fluvial style was proposed by Van der Neut and Eriksson (1999) and Eriksson et al. (2006) from their studies within the Wilgerivier Formation and the Blouberg Formation, Waterburg Group in South Africa.

3. Facies The studied stratigraphic interval is represented dominantly by granular, rarely gravelly, mixed coarse-grained sandstones and medium- to coarse-grained sandstones and subordinately by bouldery conglomerate and fine-grained sandstones/siltstones. Facies are defined on the basis of sedimentary features including

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variations in grain size, texture (matrix-supported versus clast-supported), grading types (inverse, normal and ungraded), sedimentary structures and bed geometry. Twelve sedimentary facies types have been identified on the basis of lithological and geometrical criteria and the lateral relationships with other facies. Large-scale lithofacies associations were grouped according to dominant lithotype and depositional setting (Table 1). Further, specific depositional processes and events within the fluvial system are identified through delineation ‘architectural element’s following the definitions of Miall (1978, 1985, 1996). The sand bodies have been studied by describing the measured sections and reconstructions made from large-scale photomosaics. Owing to the low angle of dip in the Par Formation, the construction of complete vertical section was possible by measuring partial sections at a location moving progressively northwards from the east–west trending basement- sedimentary contact. The work has been done in three different locations viz. Par village (78°20 2.900 E, 26°20 31.7600 N), Antri village (78°120 54.500 E, 26°40 8.200 N) and Rawat Banwari (78°40 46.4800 E, 26°30 52.7900 N); spread over 250 sq. km area (Fig. 1), where boulder conglomerates and/or poorly-sorted granular sandstones directly overlie granites and gneisses of basement. At all three localities the studied sections physically overlie the granite basement indicating that the depositional variations noticed between the sections is a reflection of control by local basin-margin physiography rather than any proximal–distal relationship. Facies association (Fa) A, conglomeratic and coarsest among all, is confined only to the Par village section delimiting margin of the basin. Also, as independent lobes, lenses or stringers constituents of Fa A (facies A4 in particular) are found embedded at different stratigraphic levels within Fa B. A better development of granular sandy Fa B is, however, noticed at the basal part of the Antri village section. Exposures of Fa C can be best noticed at the Rawat Banwari section. 4. Facies architecture Facies architecture at the studied sections was conceived not only from the mutual association of different facies types including their lateral and vertical transitions, but also from the measured vertical successions moving downdip away from the basin margin, as much as outcrop permits. Gentle topography and low bedding dip allowed lateral observations in tens to hundreds of metre scale, which helped in comprehending the spatial variations in the geometry of different depositional units. 4.1. Location 1: Par village section 4.1.1. Proximal (inner) fan Five distinctive facies belonging to facies association A (Fa A) viz. scree (A1i), massive bouldery conglomerate with chaotic clast (A1ii), inverse- to coarse-tail normal-graded pebbly conglomerate (A2), conglomerate with crude bed-parallel orientation of clasts (A3) and sheet flow conglomerate (A4) and two facies belonging to facies association B (Fa B) viz. massive (B1) and crudely stratified (B2) granular/pebbly sandstones make up 7.65 m thick section at the Par village locality (Fig. 2). Outcrop of Fa A is present only as a thin unit (<3 m in thickness) directly overlying the basement. Laterally, rocks of association A are traced not exceeding 100 m and give way to association B; only thinner counterparts of facies A4 can be observed interbedded at places. The scree breccia facies (A1; Fig. 3a) of association A, disparately coarser (pebbly and bouldery) than any conglomerate, is exclusively restricted to the contact with the basement and rapidly wedge out in the downcurrent direction. Except for a thin (Fig. 3a) basal zone where angular gravels are set within granular interclast

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Facies type Alluvial fan Facies Association A (Fa A) A1. Clast-supported boulder conglomerate

A2. Graded conglomerate

A3. Crudely stratified conglomerate

Facies Association B (Fa B) B. Massive granular sandstone

C. Rhythmic granular/ pebbly and sandy planar couplets

Description

Interpretation

Facies thickness

i. Restricted at the bottom of the Formation. Monomictic quartz gravels and boulders as a coherent mass; clasts poorly sorted and variably angular; Base often jagged as clasts penetrate into the substratum; rapidly wedge away from basement exposure ii. Ungraded matrix-infilled beds, basal bed contacts flat to scoured

Scree breccia facies (Selley, 1965). Penetration of clasts into the underlying substratum suggests loading into soft underlying sediment

0.30–0.45 m

Boulder lags from hyperconcentrated flood flows, or megaflood flow boulder beds (Dickie and Hein, 1995; Mulder and Alexander, 2001) Normal graded units represent gravelly high density flow; cohesionless debris flow (Pierson and Scott, 1985; Best, 1996) Inverse graded units resemble Sieve deposition (Major, 1997) Cohesionless debris flow (Iverson, 1997; Mulder and Alexander, 2001)

0.38–0.66 m

Sheet flow conglomerate (Enos, 1977). Clast-supported nature along with sheet-like bed geometry and intermediate axis clast imbrication indicate deposition from high energy tractive flow (Walker, 1984)

1.5–2.0 m

Hillwash deposition. Rapid settling possibly from grainflow (Shanmugam, 2000)

0.04–0.24 m

Upper flow regime tractive flow. Gradational upward transition from massive structure to planar lamination indicates that the flow evolved with decrease in sediment saturation, increase in flow shear and rapid decrease in flow depth Sheetflood couplet (SFC) deposited from sediment-charged upper flow regime flow/s. Instigated by infrequent, rapid drainage of a large volume of water from the catchment after heavy rainfall

0.09–0.14 m

Sand sheets (SS), braided fluvial channels and distributary channels (CH, CHS) with gravel bars (GB). Amalgamated channel deposits common

0.35–1.78 m

Rapid deposition from heavily loaded flow, possibly of flash flood origin

0.1–0.16 m

Bar on the channel floor (UA). Small dunes climbing the stoss of the bar (Best et al., 2003; Bose et al., 2008)

0.15–0.2 m

Transverse bank attached bar or lateral accretion on bank attached or mid channel bars (Yu et al., 2002; Ghosh et al., 2006)

0.35–0.5 m

Lower flow regime bed

0.03–0.11 m

Overbank fines. River flood plain deposits

0.01–0.03 m

Granule to pebble sized clasts; matrix or clast-supported with poorly sorted sand matrix having clay content <1%; inverse and coarse-tail normal concentration grading Granule to pebble sized clasts dominantly with bed parallel orientation and partly a-axis imbrication; poorly sorted sand matrix with clay content less than 1% Clast supported with little lateral variability in thickness; clasts are generally bed parallel or imbricated with their intermediate axis

1. Moderately sorted medium to coarse grained sheet sandstone with dispersed granules; internally massive but may give way upward gradationally to facies B2. Occasional lateral pinching of bed 2. Planar laminated sandstone in gradational contact with B1

Clast supported, poorly-sorted coarse to very coarse granule/pebble in planar beds (Gms) rhythmically interstratified with granule free medium to fine sand (Sf) resulting couplet stratigraphy; laterally traceable over meters. Bedding planes sharp but non-erosional

Braided alluvial system (Facies code adapted from Miall, 1985, 1996) Facies Association C (Fa C) Sheet-like bodies with erosive basal surfaces. Granular units internally D. Medium to coarse constituted of Gm (massive), Gh (plane lamination) and Gt (crossgrained (rarely granular) stratification); relatively sandy parts are with occasional crude cross sheet sandstone bedding (Sh, St). Incorporation of rip-up clasts from substratum E. Lensoidal conglomerate Intraformational with pebble/cobble sized clasts, frequently oversized. Matrix-supported. Bedding lenticularity in outcrop scale; planar base and convex-up top Compound cross-strata in poorly sorted sandstone. Smaller cross-strata (set F. Compound crossthickness 2.2 cm) are trough shaped and oriented roughly in opposite stratified sandstones, direction to the large cross-strata (set thickness 14 cm). Pebbles often pebbly preferentially concentrated at the base of large foresets Coarse to medium grained sandstone containing tabular cross-strata, G. Tabular cross-stratified locally with slightly asymptotic toes. Orientation roughly at an high angle coarse to medium to that of sp and St units of facies D grained sandstone H. Rippled sandstone Thin bedded sandstone with current ripples on the bedding plane. Avg. wavelength and amplitude 5.5 cm and respectively with average ripple index 0.65 cm. Commonly present at the topmost part of fining-upward cycles I. Siltstone- mudstone Infrequently present demarcating the boundaries of fining-upward cycles, laterally impersistent. Clasts ripped up from this facies are found embedded within facies D. Occasional presence of ripples

0.25–0.4 m 0.12–0.22 m 0.35–0.4 m

1.8–2.7 m

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A4. Sheet conglomerate

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Table 1 Description and interpretation of dominant sedimentary facies in the Par alluvial fan-braid plain system.

P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

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Fig. 2. Detailed measured sedimentological litholog (a) of proximal fan deposit at Par village section. Scree deposits and conglomerates of Facies association A is overlain by sandy facies of Facies association B. Photographs alongside represent rock fall deposit (b) with jagged base due to clast penetration and interbedded thin sheetflow conglomerate units (facies A4) within sediments of facies association B (c). Pie diagram (d) showing volumetric percentage of clast types within the conglomerates.

matrix, the facies is represented by gravel clasts, variably angular and compositionally monomictic (vein quartz), in a coherent mass. At places, clasts are also found penetrating into the substratum in the basal part of the facies (Fig. 2b). Conglomerates (facies types A2–4; Fig. 3b–d), in alternation with massive granular sandy intervals (facies type B1), are tabular, flat-based and laterally continu-

ous through the extent of each outcrop. They are commonly nongraded, but show local inverse grading and crude normal grading. Both matrix- and clast-supported varieties of conglomerates are with poorly-sorted feldspathic sandy matrix; matrix-supported units are by far the dominant variety. Clasts are outsized boulders of granite (15–18%), vein quartz (58–67%) or fragments of

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P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

Fig. 3. (a) Scree breccia (Facies A1i) at the base of Facies association A (Par village section). Note angular gravelly quartz clasts as a coherent mass. Granular intraclastic matrix present only at its basal part, (b) matrix-infilled boulder conglomerate (facies A1ii) with sharp, planar base, (c) inversely graded conglomerate of facies A2 documenting both size and concentration grading of clasts (hammer length 27 cm), (d) bed-parallel, imbricated clast orientation within stratified conglomerate units of facies A3 (pen length 14 cm).

sedimentary rocks (5–10%) (Fig. 2); maximum and average clast sizes recorded are12.6 cm and5.3 cm, respectively. At cases, fractured but intact bedrock slabs can be observed frozen in downward toppling condition to get incorporated within the mass flow conglomerates (Fig. 4a). Laterally as well as vertically, association A gives way to strata of association B with gradational contact. Rocks of association B comprise of two distinct facies belonging to granular poorly-sorted sandstones viz. massive (B1) and horizontally stratified (B2). Thin (max. thickness 18 cm), lenticular units of A4 conglomerates are present only infrequently (Fig. 4b). The sandstone units often show evidences of minor erosion at their bases and show pinching character in the outcrop scale (max. measured outcrop length 6.5 m). 4.1.2. Interpretation Evidences including lack of bedding, very poor size sorting, and high angularity of monomictic clasts and derivation of clasts from the basement in the immediate vicinity support origin of facies A1i as product of rock-avalanche. Significant brittle deformation but relatively lower degree of disintegration and internal mixing (except at its basal part) allowed retaining coherency within this

facies (cf. megabreccia of Blair and McPherson (1994)). Matrix-infilled conglomerates in the association (faciesA1ii) are of both colluvial slide and debris flow origin. With planar, non-erosional base facies A2 conglomerates, containing unsorted or very poorly sorted gravel fragments of shredded bedrock, represent the products of colluvial slide. Contact between the colluvium and immediate basement possibly acted as triggering glide plain. Involvement of both granite and sandstone caused wide variation in clast geometry; while granite clasts are essentially equidimensional, clasts derived from sandstones assumed their characteristic tabular shape. Hyperconcentrated flows are variously interpreted in literature as cohesive and transformed cohesive flows (Mulder and Alexander, 2001) or cohesionless debris flows and sand flows (Allen, 1997). The reverse graded facies A2 conglomerates with clast-supported character in their uppermost parts resemble sieve deposits; segregation of large clasts at the top of units possibly resulted from through flow of fines within the permeable framework of gravel clasts (Hooke, 1967; Todd, 1989; Major, 1997). Development of normal grading, though not very common in such hyperconcentrated flows, is described from both subaerial and subaqueous

Fig. 4. (a) Incorporation of angular bedrock fragments (arrowed) within normal-graded facies A2 conglomerates (lens cap diam. 5 cm), (b) thin clast-supported conglomerate units of sheet flow origin (facies A4) embedded within sediments of facies association B (facies types B1 and B2). Note occasional imbrication of clasts.

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deposits; in particular the coarse-tail normal grading in subaerial deposits is ascribed to settling of clasts within the flow during transport (Pierson and Scott, 1985; Smith, 1986; Best, 1996). Occurrence of normally graded units of facies A2 in association with crude horizontally stratified hillwash sandstones (facies B2) supports their subaerial interpretation (cf. Chakraborty et al., 2009). Ungraded facies A3 massflow conglomerate units with clasts in bed parallel orientation and imbrication in their long axes bear definite indication of flow internal shear and operation of dispersive pressure (Sarkar et al., 2008). Non-erosional base and coarse sandy matrix (with <5% mud) are most probably formed from subaerial pseudoplastic flows with high sediment concentration (sensu hyperconcentrated flow; Sohn et al., 1999; Saula et al., 2002). Further, sand: mud ratio 1:1 and presence of 8–15% disorganised gravel to boulder-sized clasts have features diagnostic for high-concentration flow character (Van Weering et al., 1998; Mulder and Alexander, 2001; Bera et al., 2008; Banerjee et al., 2008). Single boulder train of moderately rounded clasts with ungraded character in conglomerates of facies A4 possibly deposited under high competency supercritical flow, commonly associated with sheet flood events (Blair, 1999; Bose et al., 2008; Chakraborty et al., 2009). The massive and crude planar-stratified Fa B sandstones (facies types B1 and B2) at this location are products of grain flow (Shanmugam, 2000) and low-depth, high shear flows triggered by occasional rain on steep hill slopes. 4.2. Location 2: Antri village section 4.2.1. Mid fan Best exposure of Fa B is noticed at the Antri village section (maximum recorded thickness 8.5 m; Fig. 5). Sheet flood couplets (SFC; facies type C constituted of Gms and Sf; Table 1), shallow ephemeral channels (CH) constituted of pebble bars and bedforms (facies D; GB constituted of Gm, Gh and Gt) of Fa B and sheet sandstones of FA C (SS; facies D with Sh, St) in decreasing order of abundance represent the section at this location. While sediments deposited by sheet floods and pebble bars dominate the lower part of the section, sheet sandstones occupy principal volumetric share in the upper part (Fig. 5). Multistorey sheets, constituted of rhythmic inter-stratification between decimetre-thick (av. thickness 14 cm) planar-bedded, poorly-sorted pebbly, granular sandstones (Gms) and cms-thick (avg. thickness 3.5 cm) fine-grained sandstones (Sf), represent the sheet flood units (Fig. 6a). Indeed, this moderately-developed rhythmic stacking of comparatively coarse and fine beds results in a couplet stratigraphy that is the hallmark for these units. Contacts between the thick- and thin-bedded units are sharp, non-erosional and bedding continuity is traced laterally over hundreds of metres. Although massive in their general character, incipient size and concentration grading is noticed in rare instances within the Gms units (Fig. 6b). Units constituted of facies Gm, infrequently interleaved by facies Gh and commonly overlain by facies Gt, represent the GB elements (Fig. 7a and b). While laterally discontinuous diffuse pebble sheets (max. pebble size 2.9 cm) of Gh facies are internally massive or horizontally stratified with average thickness 17 cm, the cms- to decimetre-thick tabular units of Gt facies units are made up of cosets (av. set thickness 3.5 cm) of planar-curved cross-stratifications. Directional features are rare in most of the facies types; distribution of paleocurrent measurements from the Gt facies trend between 270° and 325° (Fig. 7). Within broad lenticular to sheet sandstone units of Fa C (facies D) about 40% of the structures comprise horizontal lamination (Sh), trough cross-beds (St) making up about 58% with crude cross-bedding constitute the remaining 2% (Fig. 8a and b). The thickness of SS units and horizontal laminations within them, vary between 0.8 m and 2.5 m, and 2.5 mm and 4.5 cm, respectively. Convolution

7

and low-angle truncation of laminae are common observations. The presence of parting lineation is noted rarely on the bedding surfaces. 4.2.2. Interpretation Couplets constituted of poorly-sorted granulestone and medium-grained sandstones are interpreted as the products of sediment-charged, upper flow regime sheet floods of high capacity and competence (Wells and Harvey, 1987; Blair and McPherson, 1994; Blair, 1999). Infrequent but catastrophic unconfined flows triggered by high volume of water from the catchment area following heavy rainfall may result fluid gravity flows and transfer sediments mantling the catchment slopes onto the fan through catastrophic flash floods. Several studies including flume experiments involving supercritical water flow above aggrading sand bed (Alexander et al., 2001) have suggested that the deposition from such high-discharge sheet floods is controlled principally by the migration and washout of submerged upper flow regime antidune bedforms present on the fan surface beneath trains of standing waves (Langford and Bracken, 1987; Alenander and Fielding, 1997; Blair, 1999). While the coarse member of a couplet represents deposition in a boundary-conformable plane bed during the rapid, downslope wash out phase of standing wave destruction, associated local high turbulence may cause suspension of finer sediments. On quick abatement of turbulence the fine suspended sediment accumulate upon the coarse couplet bed with a sharp, non-erosional contact. Numerous sheet flood couplets can be deposited in one flash-flood event, as documented by the accumulation of as many as 15 couplets from the sheet flood on the Roaring River fan in Colorado (Blair, 1985, 1987, 2001). Multi-storeyed sheet flood products at the basal part of the Antri section suggest their emplacement in form of an aggraded lobe in one or multiple sheet flood event/s downslope from feeder channel. The subordinate sheet sandstones interbedded with sheet flood products suggest intermittent braided fluvial palaeo-environment. Common upward-fining conglomerate-sandstone cycles, generally less than 1 m thick, point towards a fairly rapid cyclicity in discharge, possibly due to fluctuating precipitation. Flood events generating fluid gravity deposits within a vegetation-free Proterozoic palaeo-environment are thus presumed to have been intermittently followed by traction currents deposition of more sandy detritus as floods abated (Bumby, 2000; Eriksson et al., 2008). Presence of parting lineation, low-angle truncation of laminae and occurrence of scours within the sheet sandstone units support prevalent upper flow regime plane bed condition (cf., Bose and Chakraborty, 1994; Eriksson and Reczko, 1995). Occasional association of trough cross stratifications may imply intervention of low-energy conditions attributable to weak, variable current action. Signatures of such fluctuating energy and water level conditions indicate highly variable stream flow power and sediment discharge in shallow wandering streamlets from source to the basin. 4.3. Location 3: Rawat Banwari section 4.3.1. Braided fluvial Massive, horizontal- and cross-stratified granule-rich, coarsegrained, poorly sorted sandstones (facies types D, F, G, H; Table 1), clast-supported conglomerate (facies type E) and buff-coloured fine-grained sandstone/siltstone (facies type I; Table 1) constitute this section (Fig. 9); sandstones by far constitute the major volumetric proportion. Grain size within the sandstones varies from medium- to coarse-grained sand to 2–5 mm granules. Granules as well as pebbles within the conglomerates are poorly sorted, angular and of low sphericity and composed of quartz and lithic fragments. Although best exposures of this association can be

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P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

Fig. 5. Detailed measured litholog of mid fan exposed at Antri village section. Note dominance of sheet flood deposits of Fa B in the basal part and sheet sandstones (SS) of Fa C in its upper part. Paleocurrent from Gt (cross-stratified coarse, granular sandstone) and St (cross-stratified sandstone) units point north-westward.

Fig. 6. (a) Alternation between decimeter-thick massive pebbly, granular sandstone (Gms) and centimetres-thick fine/medium grained sandstone (Sf) resulting in couplet stratigraphy of sheet flood deposits (hammer length 27 cm) (b) Incipient normal grading within the Gms units.

observed at the Rawat Banwari section, sediments of this association are also present in upper part of the Antri village section. Stacked decimetre- to metre-thick fining-upward sheet-like bodies (CHS and CH elements), averaging 0.85 m in thickness and traceable in outcrop for lengths exceeding tens of metres, define this section (Fig. 10a). With planar, non-erosional or very shallow erosional/ scalloped base, each sheet begins with Gm or Gh lithofacies (cf., Miall, 1985; Eriksson and Reczko, 1995; Jones et al.,

2001) and, in turn, changes upward to Gt lithofacies and further to amalgamated sheet sandstones (SS) dominated by Sh and St lithofacies (Fig. 11a). While massive Gm and crudely-stratified Gh lithofacies are seen in mutual juxtaposition with one another, the trough cross-bedded Gt lithofacies follows either of them; within individual trough coset cross-set thickness as well as grain size decreases upward. Paleocurrent measurement from Gt and St facies units indicate north-westward direction of bedform

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P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

9

Fig. 7. Profile of Fa B (mid fan) section. (a) Photomosaic of study outcrop at the basal part of Antri village section, (b) interpretation of photomosaic. White triangle represents fining-upward trend of CH (braided or distributary channel) element. Gm represents massive pebbly sandstone, Gh represents crude horizontally laminated pebbly sandstone and Gt represents pebbly sandstones with cross-bedding (Hammer length 27 cm). Distribution of Paleocurrents from Gt is shown in the inset.

Fig. 8. Profile of Fa C (mid fan) section (a) Photomosaic illustrating architecture of sheet sandstones (SS) at the upper part of Antri village section. (b) Interpretation of photomosaic (hammer (encircled) length 27 cm). Note domination of horizontal lamination (Sh) and trough cross-bedding (St) in granule-free medium to coarse-grained sandstone. Paleocurrent from St point towards west.

migration. Although minor, lateral accretion (LA; Fig. 11b) and upstream accretion (UA; Fig. 11C) elements are also observed in association with both SS or CH elements. The accretion macroforms are only a maximum of 1.3 m long and 0.27–0.46 m thick. Some LA elements have been recognised with foresets (avg. set thickness 7.3 cm) dipping towards 45–60° and they usually consist of medium to coarse-grained sandstone, whereas UA elements are represented by set/s of compound cross-strata within which smaller cross-strata orient oppositely with the inclination of their bounding inclined planes (Fig. 11c). The small cross-stratifications, however, maintain the same north-westward orientation as

observed within the SS and CH elements. Infrequent units of conglomerate (facies E) are lenticular in geometry (rapidly wedge out with width ranging from16 cm to 1.25 m and thickness ranging from 6 cm to 0.65 m), clast-supported and polymictic in character with clasts of granite, gneiss and vein quartz; their bases are sharp, planar, non-erosional and upper surfaces discernibly convex-upward (Fig. 12). More often than not, sheet-like or discontinuous OF element drape the CHS and CH macroforms (Fig. 11b). The OF element may reach a maximum of 2.2 cm thickness and is represented by reddish fine sandstone/siltstone. Internally these fine-grained

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P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

those bound the fluvial association i.e. the contact with the basement at its base and the contact with shallow marine (tidal) succession at its top are assigned the highest order i.e. the 5th order. Surfaces bounding sheet-sandstone units, comprising of channeloverbank fine assemblage, is next lower in rank (Fig. 10b). The 3rd order bounding surfaces are the boundaries those define the contact between different macroforms e.g. channel (CH), its overbank fines (OF), lateral accretion (LA) etc. All of the boundaries are sharp and readily recognisable throughout the study area. 4.3.2. Interpretation Evidences for a braided stream interpretation includes the predominance of poorly-sorted cross-bedded medium to coarsegrained sheet sandstones having fining-upward sequences, minor silt/mudrock partings, incorporation of rip-up mud clasts within the channel deposits and consistent north-westward paleocurrent exhibiting a small variation in direction (Boggs, 1995; Bridge, 2006).Whereas sheets (35 cm–1 m thick) with planar, non-erosional base are correlated with element CHS (major sandstone sheet; Miall, 1985; Miall, 1996) those having signatures of basal incision are identified as products of channel (CH) element. The upward transition from massive/parallel laminated (Gm/Gh) to ripple laminated sandstone (Gt) within these sheets together with capping with thin layer of mudstone (OF element) is modelled as product of waning flow, as commonly observed in pre-Devonian braided river systems (Martins-Neto, 1994; Long, 2002). Further, up within individual trough coset, reduction in cross-set thickness and grain size also indicate temporally decreasing flow strength, but possibly because blocking in the upstream entry to the channels by shifting of bars (Bridge, 2006). Deposition of overbank fines (OF element) took place away from channels and mostly from suspension as the river spilled over its banks during flood (Sarkar et al., 2012). Infrequent conglomerate units having planar, non-erosional base and convex-up top represent occasional sheet flood events, which inundated the alluvial plain during high flood stages. Accretionary deposits formed during events of enhanced rate of sedimentation (cf. Bose et al., 2008; Long, 2011). Opposite orientation between the small-scale cross-strata and their bounding surfaces in the UA elements indicate bedform climb in which layers accreted on the upstream face of longitudinal bars (Mumpy et al., 2007; Long, 2011). LA elements, without much heterogeneity in their lithology, represents lateral accretion on mid channel bars or bank attached bars at high angle to the channel flow direction (Singh et al., 1993; Bridge, 2006; Sambrook Smith et al., 2009).

Fig. 9. Detailed sedimentological litholog for the Rawat Banwari section (a). Note stacked fining-upward cycles (marked by triangles). Trough cross-stratifications point towards north-westward channel bedform migration (solid rose; b), lateral accretion (LA) macroforms point towards southeast (stippled rose; c).

interbeds are either planar or ripple cross- laminated. Incorporation of clasts ripped-up from the OF element can be observed within the immediately overlying SS or CH unit. Documentation of facies and architectural elements allowed us to assess bounding surface relationships between different depositional units within the Par fluvial system. Bounding surfaces are assigned rank designations from the hierarchy of depositional units, some of which in the high order even extend beyond the channel dimensions (Miall, 1988; Miall, 1996; Holbrook, 2001). Commencing with lamina set/ cross bed set bounding surfaces as first order, coset bounding surfaces as of second order, the present study designated the surfaces bounding successively larger-scale depositional units as of higher order. Following the scheme, surfaces

5. Palaeohydraulics of Par fluvial system Various fluvial processes may operate in an alluvial fan system in different proportions, depending on climate, the nature of source terrains etc. In stratigraphic record for making distinction of such fluvial system from an independent braid plain system, workers have sought the help of reconstructed palaeohydraulic parameters. Established formulae for such reconstruction are built up from observations in modern systems (Allen, 1968; Leclair and Bridge, 2001; Ito et al., 2006) and extended in ancient river systems (Van der Neut and Eriksson, 1999; Eriksson et al., 2006, 2008; Sarkar et al., 2012). In stratigraphic record characteristic of any ancient river system can be reconstructed from width and depth of preserved channel forms or in their absence from the decompacted thickness of preserved macroforms e.g. mid-channel bar, point bar etc. However, incomplete preservation of macroforms in rock record and rare availability of lenticular, concave-up channel geometry in vegetation-free, soil-poor Precambrian systems often do not allow direct measurements of channel depth or width in field and

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P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

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Fig. 10. Stacked CHS/CH elements at the Rawat Banwari section (a). The lower sketch traces bounding surfaces of different ranks (b).

Fig. 11. (a) Architecture of Sheet Sandstone (SS) units at the upper part of Rawat Banwari section. Photomosaic of study outcrop and its interpretation. Note presence of OF element separating vertically juxtaposed CH element. (b) Lateral accretion macroform (Pen length 14 cm), (c) Upstream accretion macroform (hammer length 27 cm) having cross-stratifications dipping opposite to their set boundary inclination.

therefore indirect method needs to be applied methodologies. Data commonly collected from stratigraphic sections for using such indirect methodologies are based largely on sandstone grain-size analysis, clast sizes in channel conglomerates or set thickness of in-channel dune bedforms. Despite unavoidable errors (often as high as 50%; Eriksson et al., 2006) associated with such estimations, researchers (Miall, 1976; Eriksson et al., 2008) have unanimously agreed upon using the estimations done in ancient fluvial systems, especially when used on a comparative basis. In absence of preserved channel geometry within the Par fluvial system, we relied on field measurements of cross-bedding set thickness for undertaking palaeohydraulic calculations (cf. Sarkar et al., 2012). Measurements were carried out separately for the fluvial systems present in both Antri village and Rawat Banwari sections.

5.1. Palaeohydrological parameters Estimation from cross-bed set thickness: The mean water depth is calculated by:

h ¼ 0:086ðdm Þ

1:19

ð1Þ

where h is the mean set thickness of cross-beds in metres (Allen, 1968). The ratio between channel width and channel depth is given by:

F ¼ 225M 1:08

ð2Þ

where F is the ratio between channel width and depth, M and is the sediment load variable, i.e. the percentage of silt and clay in the channel margins, which can be assumed to be a constant of 5% for

Please cite this article in press as: Chakraborty, P.P., Paul, P. Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India. Journal of Asian Earth Sciences (2013), http://dx.doi.org/10.1016/j.jseaes.2013.09.019

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P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

Fig. 12. Polymictic facies E sheet flow conglomerate within facies association C at Rawat Banwari section. Note its planar base and convex-up top (Pen length 14 cm).

coarse bedload channels (cf. Schumm, 1968; Van der Neut and Eriksson, 1999), as also inferred in case of Par fluvial system. This gives a fixed channel width to depth ratio i.e. F = 40. The estimation of the width of channel, w, is given by:

w ¼ Fdm

ð3Þ

(Schumm, 1968). Average daily discharge (also called the mean annual discharge by some workers) is estimated by

Qm ¼ vA

ð4Þ 3

1

Qm is average daily discharge, measured in m s , and A is the mean cross-sectional surface area (approximated by dm  w) in m2; v is the velocity of water in m s1, and range between 0.5 and 1 m s1 in conditions where large subaqueous dune bedforms migrate (i.e. when cross-bedding is formed) (Leopold et al., 1964). For the purposes of present study, an intermediate velocity of 0.75 m s1 is assumed (cf. Eriksson et al., 2006). On getting Qm, mean bankfull channel depth is estimated by using the equation:

db ¼ 0:6M 0:34 Q 0:29 m

ð5Þ

where db is mean bankfull channel depth in metre (Schumm, 1969). Using db, bankfull channel width is calculated by: 1:40

wb ¼ 8:9db

ð6Þ

where wb is the bankfull channel width in metre (Leeder, 1973). This allows for a recalculation of Qm (average daily discharge) and making comparison of results with those obtained from Eq. (5), with the help of following equation:

Q m ¼ 0:027w1:71 b

ð7Þ

(Osterkamp and Hedman, 1982). Using Qm value palaeoslope (S) is estimated by the equations:

S ¼ 60M0:38 Q 0:32 m

ð8Þ

(Schumm, 1968) and by

S ¼ 30ðF 0:95 =w0:98 Þ

ð9Þ

(Schumm, 1972) Assuming that Qm is estimated only from Eq. (7) (which is likely to be more accurate than that derived from Eq. (4)), two estimates of palaeoslope can be obtained from Eqs. (8) and (9), and an approximate range of palaeoslope can be derived. Using the two values of palaeoslope from Eqs. (8) and (9), two estimations of bankfull water discharge (Qb) can be done:

Q b ¼ 4:0Ab1:21 S0:28 where Ab = db  wb (Williams, 1978).

ð10Þ

Also, the drainage (catchment) area (Ad in km2) of a river system and principle stream length (L in km, from source to depositional site) can be approximated by:

Q b ¼ A0:75 d

ð11Þ

L ¼ 1:4A0:6 d

ð12Þ

(Leopold et al., 1964). Substituting the two different values of Qb from Eqs. (11) and (12) into Eqs. (14) and (15) (A encompasses Qb) two separate values for drainage area and stream length can be calculated (Eriksson et al., 2006). 5.2. Results of reconstruction of palaeohydraulic conditions The estimated hydraulic parameters for the Par fluvial system present at Antri village and Rawat Banwari sections are presented separately in Table 2. Binary plots involving bankful water discharge (for the two values of Qb) and palaeoslope (for the two values of S) for the Antri and Rawat Banwari sections are shown separately in Fig. 13 in the backdrop of maximum gradient of rivers (0.007 m/m) and minimum gradient for alluvial fans (0.026 m/m), following Blair and McPherson (1994). It is noteworthy that despite variations in palaeoslope values obtained by the use of Eqs. (8) and (9), none of the values, irrespective of the equation used, fall below the gradient of 0.007 m/m. While many of the values, particularly those derived with the use of Eq. (8), are above the slope value 0.026 m/m and fall within the alluvial fan field, some lie within the ‘natural depositional gap’, demarcated by Blair and McPherson (1994) from their studies in modern rivers and alluvial fans. Further, it is also noticed that in contrary to the Antri section where most of the obtained palaeoslope data fall in the alluvial fan field, the data from the Rawat Banwari fluvial section dominantly fall within the ‘natural depositional gap’ earmarked by Blair and McPherson (1994). Although it is appreciated by workers that the values obtained through such palaeohydraulic analyses should not be considered as absolute, yet it is noteworthy that similar results are obtained by researchers from other Palaeoproterozoic successions (2–1.8 Ga Waterberg Group, South Africa; Van der Neut and Eriksson, 1999; Eriksson et al., 2006, 2008) and interpreted as of high-gradient braided fluvial signature, unique for the concerned Proterozoic time period. 6. Discussion 6.1. Rationale behind alluvial fan model with braided river system as lateral tributary Braided river system juxtaposed with alluvial fan is not necessarily transitional in downslope direction of the discussed fan

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W (m)

Qm (m3 s1)

db (m)

Wb (m)

Qm(1) (m3 s1)

S (m m1)

S (1) (m m1)

Qb (m3 s1)

Ab (m2)

Qb(1) (m3 s1)

Ad (km2)

Ad(1) (km2)

L (km)

L(1) (km)

Antri section 0.0385 0.508969 0.055 0.686848 0.044 0.569408 0.077 0.911292 0.033 0.447129 0.0605 0.744123 0.044 0.569408 0.055 0.686848 0.0495 0.62865 0.055 0.686848 0.044 0.569408 0.055 0.686848 0.0385 0.508969 0.0385 0.508969 0.0495 0.62865 0.044 0.569408 0.044 0.569408 0.055 0.686848 0.077 0.911292 0.055 0.686848 0.055 0.686848 0.0605 0.744123 0.044 0.569408 0.0385 0.508969 0.0385 0.508969 0.044 0.569408 0.044 0.569408 0.033 0.447129 0.0495 0.62865 0.0275 0.383614

22.90359 30.90816 25.62337 41.00812 20.12082 33.48552 25.62337 30.90816 28.28926 30.90816 25.62337 30.90816 22.90359 22.90359 28.28926 25.62337 25.62337 30.90816 41.00812 30.90816 30.90816 33.48552 25.62337 22.90359 22.90359 25.62337 25.62337 20.12082 28.28926 17.26262

8.742905 15.92191 10.94262 28.02777 6.747457 18.688 10.94262 15.92191 13.33803 15.92191 10.94262 15.92191 8.742905 8.742905 13.33803 10.94262 10.94262 15.92191 28.02777 15.92191 15.92191 18.688 10.94262 8.742905 8.742905 10.94262 10.94262 6.747457 13.33803 4.966637

1.944828 2.314087 2.075612 2.726476 1.804063 2.424121 2.075612 2.314087 2.198253 2.314087 2.075612 2.314087 1.944828 1.944828 2.198253 2.075612 2.075612 2.314087 2.726476 2.314087 2.314087 2.424121 2.075612 1.944828 1.944828 2.075612 2.075612 1.804063 2.198253 1.650666

22.58519 28.80856 24.73972 36.24369 20.33023 30.74439 24.73972 28.80856 26.81012 28.80856 24.73972 28.80856 22.58519 22.58519 26.81012 24.73972 24.73972 28.80856 36.24369 28.80856 28.80856 30.74439 24.73972 22.58519 22.58519 24.73972 24.73972 20.33023 26.81012 17.952

5.577022 8.455622 6.517315 12.52135 4.658941 9.450255 6.517315 8.455622 7.47747 8.455622 6.517315 8.455622 5.577022 5.577022 7.47747 6.517315 6.517315 8.455622 12.52135 8.455622 8.455622 9.450255 6.517315 5.577022 5.577022 6.517315 6.517315 4.658941 7.47747 3.766142

0.01878 0.016438 0.017867 0.014498 0.019893 0.015864 0.017867 0.016438 0.017098 0.016438 0.017867 0.016438 0.01878 0.01878 0.017098 0.017867 0.017867 0.016438 0.014498 0.016438 0.016438 0.015864 0.017867 0.01878 0.01878 0.017867 0.017867 0.019893 0.017098 0.021294

0.051876 0.038672 0.046474 0.029313 0.058898 0.035753 0.046474 0.038672 0.042178 0.038672 0.046474 0.038672 0.051876 0.051876 0.042178 0.046474 0.046474 0.038672 0.029313 0.038672 0.038672 0.035753 0.046474 0.051876 0.051876 0.046474 0.046474 0.058898 0.042178 0.06844

127.7519 203.9014 152.1899 316.9361 104.3783 231.036 152.1899 203.9014 177.5984 203.9014 152.1899 203.9014 127.7519 127.7519 177.5984 152.1899 152.1899 203.9014 316.9361 203.9014 203.9014 231.036 152.1899 127.7519 127.7519 152.1899 152.1899 104.3783 177.5984 82.18938

43.92431 66.66551 51.35005 98.81756 36.67702 74.52812 51.35005 66.66551 58.93543 66.66551 51.35005 66.66551 43.92431 43.92431 58.93543 51.35005 51.35005 66.66551 98.81756 66.66551 66.66551 74.52812 51.35005 43.92431 43.92431 51.35005 51.35005 36.67702 58.93543 29.63275

169.7946 259.0913 198.8993 385.9991 141.4506 290.0649 198.8993 259.0913 228.6857 259.0913 198.8993 259.0913 169.7946 169.7946 228.6857 198.8993 198.8993 259.0913 385.9991 259.0913 259.0913 290.0649 198.8993 169.7946 169.7946 198.8993 198.8993 141.4506 228.6857 113.97

643.4128 1200.126 812.5457 2160.871 491.4511 1417.662 812.5457 1200.126 998.2792 1200.126 812.5457 1200.126 643.4128 643.4128 998.2792 812.5457 812.5457 1200.126 2160.871 1200.126 1200.126 1417.662 812.5457 643.4128 643.4128 812.5457 812.5457 491.4511 998.2792 357.3449

940.2252 1651.722 1161.032 2810.488 737.0097 1920.113 1161.032 1651.722 1398.466 1651.722 1161.032 1651.722 940.2252 940.2252 1398.466 1161.032 1161.032 1651.722 2810.488 1651.722 1651.722 1920.113 1161.032 940.2252 940.2252 1161.032 1161.032 737.0097 1398.466 552.5699

67.79877 98.5517 77.98961 140.2508 57.6788 108.911 77.98961 98.5517 88.24279 98.5517 77.98961 98.5517 67.79877 67.79877 88.24279 77.98961 77.98961 98.5517 140.2508 98.5517 98.5517 108.911 77.98961 67.79877 67.79877 77.98961 77.98961 57.6788 88.24279 47.64097

85.12697 119.3687 96.61278 164.209 73.55496 130.6544 96.61278 119.3687 108.0238 119.3687 96.61278 119.3687 85.12697 85.12697 108.0238 96.61278 96.61278 119.3687 164.209 119.3687 119.3687 130.6544 96.61278 85.12697 85.12697 96.61278 96.61278 73.55496 108.0238 61.88144

Average 0.048217

0.612757

27.57405

13.15387

2.15608

26.18409

7.289088

0.0175

0.044826

173.4424

57.45217

222.9621

987.0155

1374.488

85.96077

105.2302

Rawat Banwari section 0.132 1.433395 0.143 1.533126 0.121 1.332327 0.1155 1.281248 0.1375 1.48342 0.099 1.125578 0.1485 1.582527 0.1045 1.177897 0.121 1.332327 0.11 1.229779 0.143 1.533126 0.143 1.533126 0.121 1.332327 0.099 1.125578 0.132 1.433395 0.1485 1.582527 0.11 1.229779 0.143 1.533126 0.0935 1.072791 0.1045 1.177897

64.50278 68.99066 59.95472 57.65616 66.75389 50.65099 71.21374 53.00538 59.95472 55.34006 68.99066 68.99066 59.95472 50.65099 64.50278 71.21374 55.34006 68.99066 48.27561 53.00538

69.34349 79.32853 59.90947 55.40389 74.26803 42.75871 84.52327 46.82617 59.90947 51.04203 79.32853 79.32853 59.90947 42.75871 69.34349 84.52327 51.04203 79.32853 38.84224 46.82617

3.545624 3.686681 3.398402 3.322215 3.616876 3.081756 3.755123 3.164046 3.398402 3.244144 3.686681 3.686681 3.398402 3.081756 3.545624 3.755123 3.244144 3.686681 2.997087 3.164046

52.3552 55.29423 49.33722 47.7957 53.83405 43.02367 56.73667 44.64058 49.33722 46.23067 55.29423 55.29423 49.33722 43.02367 52.3552 56.73667 46.23067 55.29423 41.37796 44.64058

23.4847 25.78376 21.21741 20.09642 24.63039 16.78818 26.94455 17.88141 21.21741 18.98429 25.78376 25.78376 21.21741 16.78818 23.4847 26.94455 18.98429 25.78376 15.70503 17.88141

0.011855 0.011506 0.012246 0.012461 0.011675 0.013199 0.011345 0.012935 0.012246 0.01269 0.011506 0.011506 0.012246 0.013199 0.011855 0.011345 0.01269 0.011506 0.013484 0.012935

0.018806 0.017606 0.020203 0.020992 0.018184 0.023833 0.017067 0.022795 0.020203 0.021852 0.017606 0.017606 0.020203 0.023833 0.018806 0.017067 0.021852 0.017606 0.024982 0.022795

642.4201 713.4884 573.1708 539.2628 677.7333 440.599 749.6737 472.9591 573.1708 505.8533 713.4884 713.4884 573.1708 440.599 642.4201 749.6737 505.8533 713.4884 408.7931 472.9591

185.6318 203.8522 167.6677 158.7876 194.7111 132.5884 213.0532 141.2448 167.6677 149.979 203.8522 203.8522 167.6677 132.5884 185.6318 213.0532 149.979 203.8522 124.0133 141.2448

731.0206 803.7408 659.413 624.0514 767.2463 519.8779 840.4957 554.2707 659.413 588.9998 803.7408 803.7408 659.413 519.8779 731.0206 840.4957 588.9998 803.7408 485.8366 554.2707

5543.178 6375.524 4761.152 4389.355 5953.126 3352.674 6810.249 3684.949 4761.152 4030.566 6375.524 6375.524 4761.152 3352.674 5543.178 6810.249 4030.566 6375.524 3033.924 3684.949

6585.259 7472.88 5739.534 5332.864 7023.923 4180.246 7931.963 4552.982 5739.534 4937.27 7472.88 7472.88 5739.534 4180.246 6585.259 7931.963 4937.27 7472.88 3819.328 4552.982

246.8217 268.434 225.2969 214.5697 257.6173 182.542 279.271 193.191 225.2969 203.8674 268.434 268.434 225.2969 182.542 246.8217 279.271 203.8674 268.434 171.9218 193.191

273.6981 295.271 252.031 241.1595 284.4958 208.3767 306.0247 219.3338 252.031 230.2609 295.271 295.271 252.031 208.3767 273.6981 306.0247 230.2609 295.271 197.3878 219.3338

h (m)

dm (m)

13

(continued on next page)

P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

Please cite this article in press as: Chakraborty, P.P., Paul, P. Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India. Journal of Asian Earth Sciences (2013), http://dx.doi.org/10.1016/j.jseaes.2013.09.019

Table 2 Palaeohydrological data derived from set thickness of cross-bedding in the fluvial system at the Antri village and Rawat Banwari sections.

257.1212 230.5645 5989.18 5004.199 677.8757 172.2735 591.8584 0.020134 0.012207 21.79808 49.96732 3.426262 62.78286 60.97531 1.355007 Average 0.12364

h = set thickness of trough cross-beds, dm = mean water depth, w = channel width, Qm = maximum instantaneous water discharge, db = mean bankfull channel depth, wb = bankfull channel width, Qm(1) = average daily discharge, S = Stream palaeoslope, s(1) = stream palaeoslope, Ad = drainage area, Qb = bankfull water discharge, Ad(1) = drainage area, Qb(1) = bankfull water discharge, L = principle stream area and L(1) = principle stream length.

L (km)

225.2969 268.434 246.8217 203.8674 214.5697 5739.534 7472.88 6585.259 4937.27 5332.864 4761.152 6375.524 5543.178 4030.566 4389.355 659.413 803.7408 731.0206 588.9998 624.0514 167.6677 203.8522 185.6318 149.979 158.7876 573.1708 713.4884 642.4201 505.8533 539.2628 0.020203 0.017606 0.018806 0.021852 0.020992 0.012246 0.011506 0.011855 0.01269 0.012461 21.21741 25.78376 23.4847 18.98429 20.09642 49.33722 55.29423 52.3552 46.23067 47.7957 3.398402 3.686681 3.545624 3.244144 3.322215 59.90947 79.32853 69.34349 51.04203 55.40389 1.332327 1.533126 1.433395 1.229779 1.281248 0.121 0.143 0.132 0.11 0.1155

59.95472 68.99066 64.50278 55.34006 57.65616

Ad(1) (km2) Ad (km2) Qb(1) (m3 s1) Ab (m2) Qb (m3 s1) S (1) (m m1) S (m m1) Qm(1) (m3 s1) Wb (m) db (m) Qm (m3 s1) W (m) dm (m) h (m)

Table 2 (continued)

252.031 295.271 273.6981 230.2609 241.1595

P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

L(1) (km)

14

system but may also act as tributaries for the fan. This is the typical setting in rift and pull-apart basins and in glacial valleys (Rust, 1978; McPherson et al., 1987). Although the alluvial fan and braided-river facies may occur side by side, the alluvial fan system is almost entirely controlled from the fan catchment basin, with relatively little control by, or relationship to the braided river system. Triggered by rapid snow melting or heavy rainfall, catastrophic supercritical flow of water and sediment discharges down the sediment-mantled steep slopes, either in form of unconfined sheet floods or as debris flows and hyperconcentrated flows along short-length, low-order streams, facilitates fan sedimentation. Subcritical flows along bed load dominated shallow, wandering channels fed from gentle-sloping large discharge area characterise the proximal pebbly braid plain systems (Jones et al., 2001; Miall, 2006; Long, 2011). Studies in climatically variable modern settings have also shown that in contrast to the high humidity wet climate fan systems where debris flows dominate the sediment transfer process, the arid climate dry fans are dominated by fluvial processes (Mack and Rasmussen, 1984; Harvey, 2012). Absence of vegetation and well-developed soil cover allowed operation of debris flows and hyperconcentrated flows with equal preponderance in Proterozoic braided fluvial systems and hence, pose difficulty in climatic distinction. In corroboration with field observation, the independent estimations of palaeoslope values, stream length, water velocity and bankful water discharge with the use of palaeohydraulic analyses, therefore, can allow workers narrowing down their interpretations in favour of either fan or fluvial systems. Clusters of angular, poorly sorted, granular to bouldery granite and gneiss fragments in deposits of Fa A resemble talus or colluvial cone deposition, occasionally as rock falls, at the frontal parts of bedrock cliffs. However, rock fall deposition was aerially restrictive and the Par fan system was dominantly fed by fluid gravity flows and low-order streamlet flows generated on the colluvial slopes. The scree, colluvial slide and debris flow deposits at the Par village section represent the thin proximal fan products deposited below the intersection point between the fan surface and water table (e.g. Talbot and Williams, 1979). The assemblage dominated by sheet flood and streamlet facies with subordinate sieve deposits and rare debris flow deposits at the Antri village section represent the mid-fan region at or above the intersection point (cf. Rahn, 1967; Wendland et al., 2012). An overall dominance of sheet flood and braid streamlet products prompted us to interpret the Par alluvial fan as a dry-climate fan, dominantly represented by its mid fan zone. Up in the stratigraphic column at the Antri village section the thin fluvial deposits with intervening sheet flood are identified as distal medial fan products. Laterally impersistent streamlet facies recording rare preservation of thin (avg. set thickness 4.5 cm) cross-bed sets indicate shallow, low-velocity flow within the fluvial system, a condition commonly associated with dry fans. Also, rarity of trough cross-bedded facies indicates that transportation of sand and gravel as dune bedforms was not a common process in the fluvial part of Par alluvial fan. That the Par fan was primarily built by rare, catastrophic sheet floods typified by supercritical flow conditions is attested by the dominance of facies C couplets and facies B1 hillwash sandstones. The palaeohydraulic results corroborate this contention. In contrast, we are inclined to interpret the fluvial deposit that directly overlies the gneissic basement at the Rawat Banwari section as an independent braided fluvial system that may have acted as a tributary for the Par fan system. Higher bankful water discharge values (440.59–749.67 m3 s1; dominantly above 500 m3 s1) for the fluvial system at this location compared to that for the fluvial system at the Antri section (82.18–316.93 m3 s1; dominantly below 200 m3 s1) support this contention. Higher

Please cite this article in press as: Chakraborty, P.P., Paul, P. Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India. Journal of Asian Earth Sciences (2013), http://dx.doi.org/10.1016/j.jseaes.2013.09.019

P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

15

Fig. 13. Binary plot of palaeoslope (S) and mean annual bankful discharge values (Qb) calculated for the fluvial systems present at Antri (a) and Rawat Banwari (b) sections. The two values of S (Eq. (8) (S) and Eq. (9) (S1)) enable two estimates of Qb. Maximum gradient for rivers (0.007 m/m) and minimum gradient for alluvial fan (0.026 m/m) are shown after Blair and McPherson (1994). Note palaeoslope values from the Antri section dominantly fall in alluvial fan field whereas those from Rawat Banwari section fall dominantly within ‘natural depositional gap’.

palaeoslope values estimated for the braided system, falling mostly between the maximum found in rivers and the minimum applicable to alluvial fans, corroborate well with the high gradient river styles noted by workers who published on riverine deposits of this time period (2–1.9 Ga Waterberg group, South Africa, Eriksson et al., 2006, 2008). That the fluvial system might have acted as tributary for the laterally adjacent fan system is suggested from the consistent north-westward paleocurrent noticed in the fluvial deposits of both Rawat Banwari and Antri village sections.

loss of flow slope gradient. The thin (6 m) alluvial package at the Par village section and successively thicker packages at the Antri (12 m) and Rawat Banwari (16 m) sections correspond with the successively lower slope gradients inferred from these sections i.e. Par and Antri village represents the proximal and middle part of the alluvial fan, respectively in high-gradient setting and Rawat Banwari represents braided fluvial system in strike-wise low-gradient parts of rifted basin margin.

6.2. Variation in basin margin physiography

6.3. Paleoproterozoic atmosphere and possible controls on depositional system

Basin physiography and its control on variability of volume and grain-size of supplied sediment have been increasingly recognised as important controls on the temporal and spatial evolution of depositional systems (Schlager, 1991; Gawthorpe et al., 1994; Church and Gawthorpe, 1997; Mackintosh and Robertson, 2012). Out of the three studied locations, the basin margin is interpreted as steep at the Par village location where the base-of-slope clastic sedimentary rocks are coarsest and include products of free fall and rock avalanche processes. Although limited, occurrence of these avalanche and scree deposits at the base of this section suggest formation of slope steeper than angle-of-repose (cf. Bose et al., 2008). Steep slope, however, did not last long and rapid decline in slope below that of the angle of repose is recorded by predominant occurrence of mass flows and traction current deposits in remaining part of this section. Nonetheless, inter-layered within Fa B association occurrence of thin A4 facies deposits, well above the base of the section, at this locality indicates continuation of occasional uplift of basement rocks through the par depositional history. The absence of conglomeratic proximal deposits at the Antri and Rawat Banwari sections are definite indication in favour of slope stabilisation at these localities as well as expansion of drainage through networking of low-order streams. However, dominant sheet flood deposition at the basal part of Antri section indicates relatively higher slope compared to that of the Rawat Banwari section; fluid gravity flows entraining clay-deficient colluvium that mantled the slope possibly triggered the sheet floods (Blair, 1999; Bose et al., 2008). The laterally discontinuous stream deposits with scanty presence of trough cross-stratified bed at the Antri section suggests shallow, ephemeral, high velocity flows in braided washes and gullies, not conducive to the formation of dune bedforms. In contrast, the stacked laterally continuous braided stream successions with defined fining-upward character and presence of fine-grained overbank sediment at the Rawat Banwari section suggest increasingly steady and relatively weaker channel flow with

A large school of thought agrees on overall greenhouse condition in the early Precambrian and concomitant high weathering of labile material (Corcoran and Mueller, 2004; Eriksson et al., 2005, 2009, 2013). Any tectonic relief created in such climatic condition would have suffered rapid winnowing under aggressive weathering and in the process preferentially generated sand-size grains compared to pebbles and boulders. Acknowledging this effect, Van der Neut and Eriksson (1999) advocated that such size bias ingenerated detritus limited in alluvial fan formation close to the source and instead, facilitated high-gradient braided channels in fault-controlled drainage areas. Alluvial fans, if present, were laterally restricted and only localised very close to the available reliefs, commonly flanked by braided channel systems in both strike-wise and downslope directions. Along the margin of Par basin, the crystalline granite basement acted as a facilitator in the weathering process and generated relatively gentler slopes in otherwise fault-bounded rift margin. That there was severe weathering in the immediate basement of Gwalior basin is also advocated by Absar et al. (2009) from the geochemical signatures of Gwalior clastics. Preponderance of granular and sandy (occasionally pebbly) sediments in the Par alluvial system, with boulders and pebbles restricted only to the basal part of the Par village section, also suggest that the drainage basin was dominantly colluvium covered and gently sloping (1–7°) bevelled plain. Steep cliff exceeding angle of repose was restricted only to the Par village area. It is also true that while alluvial fan sequences are likely to be aerially restricted in such aggressive climatic conditions, braided fluvial systems used to occupy higher gradient slopes unlike modern day rivers. ‘Ponding’ and temporary accumulation of argillaceous sediment within the Precambrian fluvial systems is considered by Eriksson et al. (2009) as the prime reason behind local steepening of palaeoslope. Although limited, the definite occurrence of overbank fines (OF) within the Rawat Banwari fluvial section supports this view. An alternative suggestion, however, is

Please cite this article in press as: Chakraborty, P.P., Paul, P. Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India. Journal of Asian Earth Sciences (2013), http://dx.doi.org/10.1016/j.jseaes.2013.09.019

16

P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

a higher rate of sediment bypassing in the Precambrian (Sarkar et al., 2012). The measured sections at all the three studied locations reveal shallow marine associations succeeding the continental (subaerial) ones up the stratigraphic column and thereby suggesting an overall retrogradational stacking pattern. In the stratigraphic record such fining-upward alluvial–coastal define transgressive sequences and are interpreted as a signature of deepening (Bourgeois, 1980; Emery and Myers, 1996). For an alluvial fan- braid plain system such deepening-up tendency is related either to declining sediment supply caused by retreat of scarp front and lowering of source area relief (Kingsley, 1984; Rigsby, 1994) or to increased accommodation as high rates of subsidence outpaced the sediment flux (Benvenuti, 2003; Rainbird et al., 2003) or a combination of both. A gradual steady decrease in grain size up the stratigraphic column in the studied sections strongly suggests progressing erosion of the source area and in turn, decreasing supply of detritus. The fining-upward stacking pattern within the Par alluvial system closely resembles that of the fault-bounded Baker Lake half-graben system, Churchil Province, Canada (Rainbird et al., 2003) but at a different scale. 7. Conclusions 1. Despite limitations imposed by widely spaced sections, it has been possible to reasonably deduce the detailed depositional systems viz. alluvial fan and laterally co-existing braid plain system in the basal part of the Par Formation, the Gwalior Group. Considering the relative dominance of rock avalanche, gravity flow and channel flow processes, two anatomical parts could be delineated within the Par alluvial fan, i.e., inner and middle fan, respectively. Along-strike the occurrence of stacked, metre-thick tabular sheet sandstonesthat rest over granitic basement enabled us to infer that the fan system is laterally discontinuous and associated with braided river plain, which acted as tributary for the fan. 2. The outcrop based interpretations found support in palaeoslope estimations carried out through deductive palaeohydraulics. While palaeoslopes estimated from mid fan streamlet deposits plot within the alluvial fan field, the values derived from the braid plain deposits fall dominantly within the ‘natural depositional gap’, which separates alluvial fan (palaeoslopes > 0.026 m/m) and fluvial deposits (palaeoslopes < 0.007 m/m) in slope-bankful discharge binary diagram. 3. Steep palaeoslope values from the Par braid plain system are generally consistent with values obtained from other Precambrian braided stream deposits, in general, and particularly in the Palaeoproterozoic river systems. The present study thus reaffirms the validity of high gradient pre-vegetative river systems in Precambrian Era that often fall within the ‘natural depositional gap’ or even transgress the boundary of alluvial fan field demarcated by studies of modern depositional systems. 4. Pre-dominance of fluvial activity over debris-flow within the alluvial fan allowed the interpretation of dry climatic condition. This is well consistent with arid to semi-arid settings interpreted by Condie (1997) from the Proterozoic rock record that postdates 2.3 Ga. 5. Pre-dominance of granular and sandy (occasionally pebbly) sediments within the Par clastic system is suggestive of a colluvium covered gently sloping bevelled plain as the dominant drainage basin, with steep cliff/s present only locally. The north-westerly paleocurrent pattern recorded in the fluvial system is indicative of a source area in the south and/or southeast. 6. The overall fining-upward facies sequence that leads to shallow marine clastics above both alluvial fan and braid plain succes-

sions suggests a retrogradational evolution under the combined effect of the source area denudation and rise in relative sea level.

Acknowledgements The authors are thankful to University Grants Commission, Government of India for providing necessary funding. Department of Geology, University of Delhi had provided the necessary infrastructural facilities. Authors also express their sincere thanks to Mr. Subhojit Saha, Mr. Arvind Singh and Mr. Priyabrata Das for their assistance in field time to time. References Absar, N., 2005. Geology and Geochemistry of Paleoproterozoic Gwalior Group Sediments, Bundelkhand Craton, Central India: Implications for Provenance, Depositional Environment, Tectonic Setting and Evolutionary Trend of Upper Continental Crust. Unpublished Ph.D. Thesis. Aligarh Muslim University, Aligarh, India, p. 189. Absar, N., Raza, M., Roy, M., Naqvi, S.M., Roy, A.K., 2009. Composition and weathering conditions of Paleoproterozoic upper crust of Bundelkhand craton, Central India: records from geochemistry of clastic sediments of 1.9 Ga Gwalior Group. Precambrian Research 168, 313–329. Adil, S.H., 1999. Studies of textural parameters for clastic sediments of Gwalior group of rocks. In: Proc.XVI – Convention, Indian Association of Sedimentologists, 4. Alenander, J., Fielding, C., 1997. Gravel antidunes in the tropical Burdekin River, Queensland, Australia. Sedimentology 44, 327–337. Alexander, J., Bridge, J.S., Cheel, R.J., Leclair, S.F., 2001. Bedforms and associated sedimentary structures formed under supercritical water flows over aggrading sand beds. Sedimentology 48 (1), 133–152. Allen, J.R.L., 1968. Current Ripples. North-Holland Publishing Corporation Amsterdam, p. 433. Allen, P.A., 1997. Earth Surface Processes. Blackwell, Oxford, p. 404. Banerjee, S., Jeevankumar, S., Eriksson, P.G., 2008. Mg-rich ferric illite in marine transgressive and highstand systems tracts: examples from the Paleoproterozoic SemriGroup, central India. Precambrian Research 162, 212– 226. Benvenuti, M., 2003. Facies analysis and tectonic significance of lacustrine fandeltaic successions in the Pliocene–Pleistocene Mugello Basin, Central Italy. Sedimentary Geology 157, 197–234. Bera, M.K., Sarkar, A., Chakraborty, P.P., Loyal, R.S., Sanyal, P., 2008. Marine to continentaltransition in Himalayan foreland. Geological Society of America Bulletin 120 (9–10), 1214–1232. Best, J.L., 1996. The fluid dynamics of small-scale alluvial bedforms. In: Carling, P.A., Dawson, M.R. (Eds.), Advances in Fluvial Stratigraphy. John Wiley and Sons, New York, pp. 67–125. Best, J.L., Ashworth, P.J., Bristow, C.S., Roden, J., 2003. Three-dimensional sedimentary architecture of a large, mid-channel Sand Braid Bar, Jamuna River, Bangladesh. Journal of Sedimentary Research 73 (4), 516–530. Blair, T.C., 1985. Depositional chronology, sedimentary processes, and the resulting vertical stratification sequences in the Roaring River alluvial fan, Rocky Mountain National Park, Colorado. In: Flores, R.M., Harvey, M.D. (Eds.), Field Guidebook to Modern and Ancient Fluvial Systems in the United States. Proceedings. Third International Fluvial Conference. Colorado State University, Fort Collins, CO, pp. 96–101. Blair, T.C., 1987. Tectonic and hydrologic control on cyclic alluvial fan, fluvial, and lacustrine rift-basin sedimentation, Jurassic–lowermost Cretaceous Todos Santos Formation, Chiapas, Mexico. Journal of Sedimentary Petrology 57, 845–862. Blair, T.C., 1999. Sedimentology of gravelly Lake Lahontan high-stand shoreline deposits, Churchill Butte, Nevada. Sedimentary Geology 123, 187–206. Blair, T.C., 2001. Outburst flood sedimentation on the proglacial Tittle canyon alluvial fan, Owens Valley, California, U.S.A.. Journal of Sedimentary Research 71, 658–680. Blair, T.C., McPherson, J.G., 1994. Alluvial fans and their natural distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies assemblages. Journal of Sedimentary Research A 64, 450–489. Boggs, S., Jr., 1995. Principles of Sedimentology and Stratigraphy, second ed. Prentice-Hall, Inc., New Jersy, p. 774. Bose, P.K., Chakraborty, P.P., 1994. Proterozoic upper Rewa Sandstone, Maihar, India. Sedimentary Geology 89, 285–302. Bose, P.K., Sarkar, S., Mukhopadhyay, S., Saha, B., Eriksson, P., 2008. Precambrian basin-margin fan deposits: Mesoproterozoic Bagalkot Group, India. Precambrian Research 62 (1), 264–283. Bose, P.K., Eriksson, P.G., Sarkar, S., Wright, P., Samanta, P., Mukhopadhyay, S., Mandal, S., Banerjee, S., Altermann, W., 2012. Sedimentation patterns during the Precambrian: a unique record? Marine and Petroleum Geology 33, 34–68.

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P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx Bourgeois, J., 1980. A transgressive shelf sequence exhibiting hummocky cross stratification: the Cape Sebastian Sandstone (upper Cretaceous), southwestern Oregon. Journal of Sedimentary Petrology 50, 681–702. Bridge, J.S., 2006. Fluvial facies models: recent developments. In: Posamentier, H.W., Walker, R.G. (Eds.), Facies Models Revisited. SEPM special Publication 84, 85–170. Bumby, A.J., 2000. The Geology of the Blouberg Formation, Waterberg and Soutpansberg Groups in the area of Blouberg Mountain, Northern Province, South Africa. PhD Thesis. University Pretoria Unpublished, p. 325. Chakraborty, P.P., Sarkar, A., Das, K., Das, P., 2009. Alluvial fan to storm-dominated shelf transition in the Mesoproterozoic Singhora Group, Chhattisgarh Supergroup, Central India. Precambrian Research 170, 88–106. Church, K.D., Gawthorpe, R.L., 1997. Sediment supply as a control on the variability ofsequences: an example from the late Namurian of northern England. Journal of the Geological Society, London 154, 55–60. Condie, K.C., 1997. Plate Tectonics and Crustal Evolution, fourth ed. Butterworth Heinemann, Oxford. Corcoran, P.L., Mueller, W.U., 2004. Aggressive Archaean weathering. In: Eriksson, P.G., Altermann, W., Nelson, D.R., Mueller, W.U., Catuneanu, O. (Eds.), The Precambrian Earth: Tempos and Events. Elsevier, Amsterdam, pp. 494–504. Corcoran, P.L., Mueller, W.U., Chown, E.H., 1998. Climatic and tectonic influences on fan deltas and wave- to tide-controlled shoreface deposits: evidence from the Archean Keskarrah Formation, Slave Province. Canadian Sedimentary Geology 120, 125–152. Crawford, A.R., 1970. The Precambrian geochronology of Rajasthan and Bundelkhand, northern India. Canadian Journal of Earth Sciences 7, 91–110. Crawford, A.R., Compston, W., 1971. The Age of the Vindhyan System of Peninsular. Donaldson, J.A., de Kemp, E.A., 1998. Archean quartz arenites in the Canadian Shield: examples from the Superior and Churchill Provinces. Sedimentary Geology 120, 153–176. Dickie, J.R., Hein, F.J., 1995. Conglomeratic fan deltas and submarine fans of the Jurassic Laberge Group, Whitehorse Trough, Yukon Teritorry, Canada: fore-arc sedimentation and unroofing of a volcanic island arc complex. Sedimentary Geology 98, 263–292. Els, B.G., 1990. Determination of some palaeohydraulic parameters for a fluvial Witwatersrand succession. South African Journal of Geology 93, 531–537. Emery, D., Myers, K.J., 1996. Sequence Stratigraphy. Blackwell, Oxford, UK, p. 297. Enos, P., 1977. Flow regimes in debris flow. Sedimentology 24 (1977), 133–142. Eriksson, P.G., Reczko, B.F.F., 1995. The sedimentary and tectonic setting of the Transvaal Supergroup floor rocks to the Bushveld complex. Journal of African Earth Science 21, 487–504. Eriksson, P.G., Altermann, W., Catuneanu, O., Van der Merwe, R., Bumby, A.J., 2001. Major influences on the evolution of the 2.67–2.1 Ga Transvaal basin, Kaapvaal craton. Sedimentary Geology 141–142, 205–231. Eriksson, P.G., Catuneanu, O., Els, B.G., Bumby, A.J., Van Rooy, J.L., Popa, M., 2005. Kaapvaal craton: changing first- and second-order controls on sea level from c. 3.0 Ga to 2.0 Ga. Sedimentary Geology 176, 121–148. Eriksson, P.G., Bumby, A.J., Brümer, J.J., van der Neut, M., 2006. Precambrian fluvial deposits: enigmatic palaeohydrological data from the c. 2-1.9 Ga. Waterberg group, South Africa. Sedimentary Geology 190, 25–46. Eriksson, P.G., Long, D., Bumby, A., Eriksson, K., Simpson, E., Catuneanu, O., Claassen, M., Mtimkulu, M., Mudziri, K., Brume, J., Van der Neut, M., 2008. Palaeohydrological data from the c 2.0 to 1.8 Ga. Waterberg Group, South Africa: a discussion of a possibly unique Palaeoproterozoic fluvial style. South African Journal of Geology 111, 281–304. Eriksson, P.G., Rautenbach, C.J.deW., Wright, D.T., Bumby, A.J., Catuneanu, O., Mostert, P., van der Neut, M., 2009. Possible evidence for episodic epeiric marine and fluvial sedimentation (and implications for palaeoclimatic conditions), c. 2.3–1.8 Ga, Kaapvaal craton, South Africa. Palaeogeography, Palaeoclimatology, Palaeoecology 273, 153–173. Eriksson, P.G., Banerjee, S., Catuneanu, O., Corcoran, P.L., Eriksson, K.A., Hiatt, E.E., Laflamme, M., Lenhardt, N., Long, G.F.D., Miall, A.D., Mints, M.V., Pufahl, P.K., Sarkar, S., Simpson, E.L., Williams, G.E., 2013. Secular changes in sedimentation systems and sequence stratigraphy. Gondwana Research 24 (2), 468–489. Gawthorpe, R.L., Leeder, M.R., 2000. Tectono-sedimentary evolution of active extensional basins. Basin Research 12, 195–218. Gawthorpe, R.L., Fraser, A.J., Collier, R.E.Ll., 1994. Sequence stratigraphy in active extensional basins: implications for the interpretation of ancient basin fills. Marine and Petroleum Geology 11, 642–658. Ghosh, P., Sarkar, S., Maulik, P., 2006. Sedimentology of a muddy alluvial deposit: Triassic Denwa Formation, India. Sedimentary Geology 191 (1–2), 3–36. Harvey, A.M., 1990. Factors influencing Quaternary fan development in Southeast Spain. In: Rachocki, A.H., Church, M. (Eds.), Alluvial Fan – A Field Approach. Willey, New York, pp. 247–270. Harvey, A.M., 2012. The coupling status of alluvial fans and debris cones: a review and synthesis. Earth Surface Processes and Landforms 37, 64–76. Hashimoto, A., Oguchi, T., Hayakawa., Lin, Y., Zhou, Saito, K., Waskelewicz, T.A., 2008. GIS analysis of depositional slope change at alluvial-fan toes in Japan and the American southwest. Geomorphology 100, 120–130. Heron, A.M., 1922. The Gwalior and Vindhyan System in south eastern Rajasthan, Memoir. Geological Survey of India 45, 129–184. Holbrook, J., 2001. Origin, genetic interrelationships, and stratigraphy over the continuum of fluvial channel-form bounding surfaces: an illustration from middle Cretaceous strata, southeastern Colorado. Sedimentary Geology 144, 179–222. Hooke, R.L.B., 1967. Processes on arid-region alluvial fans. Geology 75, 438–460.

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Ito, M., Matsukawa, M., Saito, T., Nichols, D.L., 2006. Facies architecture and palaeohydrology of a synrift succession in the Early Cretaceous Choyr Basin, southeastern Mongolia. Cretaceous Research 27, 226–240. Iverson, R.M., 1997. Physics of debris flows. Reviews in Geophysics 35, 245–296. Jones, S.J., Frostick, L.E., Astin, T.R., 2001. Braided stream and flood plain architecture: the Rio Vero Formation, Spanish Pyrenees. Sedimentary Geology 139, 229–260. Kingsley, C.S., 1984. Dagbreek fan delta: an alluvial placer to pro-delta sequence in the Proterozoic Welkom goldfield Witwatersrand south Africa. In: Koster, E.H., Steel, R.J. (Eds.), Sedimentology of Gravels and Conglomerates, vol. 10. Canadian Society of Petroleum Geology, Memoir, pp. 321–330. Langford, R., Bracken, B., 1987. Medano Creek, Colorado, a model for upper-flowregime fluvial deposition. Journal of Sedimentary Petrology 57, 863–870. Leclair, S.F., Bridge, J.S., 2001. Quantitative interpretation of sedimentary structures formed by river dunes. Journal of Sedimentary Research 71 (5), 713–716. Leeder, M.R., 1973. Fluviatile fining-upwards cycles and the magnitude of palaeochannels. Geological Magazine 110, 265–276. Leeder, M.R., 2011. Tectonic sedimentology: sediment systems deciphering global to local tectonics. Sedimentology. The journal of the International Association of Sedimentologists 58, 2–56. Leopold, L.B., Wolman, G.M., Miller, J.P., 1964. Fluvial Processes in River Geomorphology. Freeman, San Francisco, United States of America, p. 522. Long, D.G.F., 2002. Aspects of Late Paleoproterozoic fluvial style: the Uairen Formation. Roraima Supergroup, Venezuela. In: Alterman, W., Corcoran, P. (Eds.), Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems: International Association of Sedimentologists, Special Publication 33, 323–338. Long, D.G.F., 2011. Architecture and Depositional Style of Fluvial Systems Before Land Plants: A Comparison of Precambrian, Early Palaeozoic, and Modern River Deposits from River to Rock Record: The Preservation of Fluvial Sediments and Their Subsequent Interpretation. Society for Sedimentary Geology, Special Publication No. 97, pp. 37–61. Mack, G.H., Rasmussen, K.A., 1984. Alluvial-fan sedimentation of the Cutler Formation (Permo-Pennsylvanian) near Gateway, Colorado. Geological Society of America Bulletin 95, 109–116. Mackintosh, P.W., Robertson, A.H.F., 2012. Late Devonian–Late Triassic sedimentary development of the central Taurides, S Turkey: implications for the northern margin of Gondwana. Gondwana Research 21, 1089–1114. Major, J.J., 1997. Depositional processes in large-scale debris flow experiments. Journal of Geology 105, 345–366. Mallikharjuna Rao, J., Poornachandra Rao, G.V.S., Widdowson, M., Kelley, S.P., 2005. Evolution of Proterozoic mafic dyke swarms of the Bundelkhand Granite Massif, Central India. Current Science 88, 502–506. Martins-Neto, M.A., 1994. Braidplain sedimentation in a Proterozoic rift basin: the SaoJoaoda Chapada Formation, southeastern Brazil. Sedimentary Geology 89, 219–239. Mathur, S.M., 1982. Precambrian sedimentary sequences of India: their geochronology and correlation. Precambrian Research 18, 139–144. McPherson, J.G., Shanmugam, G., Moiola, R.J., 1987. Fan-deltas and braid deltas: varieties of coarse-grained deltas. GSA Bulletin 99 (3), 331–340. Miall, A.D., 1976. Palaeocurrent and palaeohydrologic analysis of some vertical profiles through a Cretaceous braided stream deposit, Bank Island, Arctic Canada. Sedimentology 23, 459–483. Miall, A.D., 1978. Lithofacies types and vertical profile models in braided river deposits: a summary. In: Miall, A.D. (Ed.), Fluvial Sedimentology. Canadian Society of Petroleum Geologist Memoir 5, 597–604. Miall, A.D., 1985. Sedimentation on an early Proterozoic continental margin under glacial influence: the Gowganda Formation (Huronian), Elliot Lake area, Ontario, Canada. Sedimentology 32, 763–788. Miall, A.D., 1988. Reservoir heterogeneities in fluvial sandstones: lessons from outcrop studies. Bulletin American Association of Petroleum Geology 72, 682– 697. Miall, A.D., 1996. The Geology of Fluvial Deposits: Sedimentary Facies, Basin Analysis and Petroleum Geology. Springer, New York, p. 582. Miall, A.D., 2006. Geology of Fluvial Deposits. Springer-Verlag, p. 582. Mondal, M.E.A., Zainuddin, S.M., 1996. Evolution of Archean–Palaeoproterozoic Bundelkhand massif, Central India evidence from granitoid geochemistry. Terra Nova 8, 532–539. Mondal, M.E.A., Goswami, J.N., Deomurari, M.P., Sharma, K.K., 2002. Ion microprobe 207 Pb/206Pb ages of zircons from the Bundelkhand Massif, northern India: implications for crustal evolution of the Bundelkhand–Aravalli supercontinent. Precambrian Research 117, 85–100. Mueller, W.U., Corcoran, P.L., 1998. Characteristics of pre-vegetational, lateorogenicbasins: examples from the Archean Superior Province, Canada. Sedimentary Geology 120, 177–204. Mulder, T., Alexander, J., 2001. The physical character of subaqueous sedimentary density flows and their deposits. Sedimentology 48, 269–299. Mumpy, A.J., Jol, H.M., Kean, W.F., Isbell, J.L., 2007. Architecture and sedimentology of an active braid bar in the Wisconsin River based on 3-D ground penetrating radar. GSA Special Papers 432, 111–131. Nemec, W., Steel, R.J., 1988. What is fan delta and how do we recognize it? In: Nemec, W., Steel, R.J. (Eds.), Fan Deltas: Sedimentology and Tectonic Setting. Blackie, Glasgow, pp. 3–13. Osterkamp, W.R., Hedman, E.R., 1982. Perennial Streamflow Characteristics Related to Channel Geometry and Sediment in the Missouri River Basin. Professional Paper, United States of America, Geological Survey 1242, p. 37.

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P.P. Chakraborty, P. Paul / Journal of Asian Earth Sciences xxx (2013) xxx–xxx

Pierson, T.C., Scott, K.M., 1985. Downstream dilution of a lahar: transition from a debris flow to hyperconcentrated stream flow. Water Resource Research 21, 1511–1524. Rahn, P.H., 1967. Sheetfloods, streamfloods, and the formation of sediments. Annaul Association American Geographers 57, 593–604. Rainbird, R.H., Hadlari, T., Aspler, L.B., Donaldson, J.A., Le Cheminant, A.N., Peterson, T.D., 2003. Sequence stratigraphy and evolution of the Paleoproterozoic intracontinental Baker Lake and Thelon basins, western Churchill Province, Nunavut, Canada. Precambrian Research 125, 21–53. Ram Mohan, M., Singh, S.P., Santosh, M., Siddiqui, M.A., Balaram, V., 2012. TTG suite from the Bundelkhand Craton, Central India: geochemistry, petrogenesis and implications for Archean crustal evolution. Journal of Asian Earth Sciences 58, 38–50. Ramakrishnan, M., Vaidyanadhan, R., 2010. Geology of India. Geological Society of India, Banglore1, p. 461. Reading, H.G., Orton, G.J., 1991. Sediment calibre: a control on facies models with special reference to deep sea depositional systems. In: Muller, D.W., McKenzie, J.A., Weissert, H. (Eds.), Controversies in Modern Geology. Academic Press, pp. 85–111. Rigsby, C.A., 1994. Deepening-upward sequences in Oligocene and lower Miocene fan-delta deposits, Western Santa Ynez mountains, California. Journal of Sedimentary Research B64, 380–391. Roy, A.K., Absar, N., Kumar, S., Sharma, R., Rai, S.D., Parihar, P.S., 2005. Some observationon lithostratigraphy and uranium potential of Gwalior Group of rocks, Gwalior District, MP. In: Proc. ‘International Conference on Precambrian Crustalgrowth and Tectonism’. Bundelkhand University, Jhansi, pp. 299–301. Rust, B.R., 1978. Depositional models for braided alluvium. Canadian Society of Petroleum. Geology Memoir 5, 605–625. Saito, K., Oguchi, T., 2005. Slope of alluvial fans in humid regions of Japan. Taiwan and the Philippines: Geomorphology 70, 147–162. Sambrook Smith, G.H., Ashworth, P.J., Best, J.L., Lunt, I.A., Orfeo, O., Parsons, D.R., 2009. The sedimentology and alluvual arquitecture of a large braid bar, Rio Paraná, Argentina. Journal of Sedimentary Research 79, 629–642. Sarkar, S., Bose, P.K., Samanta, P., Sengupta, P., Eriksson, P.G., 2008. Microbial mat mediated structures in the Ediacaran Sonia Sandstone, Rajasthan, India, and their implications for proterozoic sedimentation. Precambrian Research 162, 226–248. Sarkar, S., Samanta, P., Mukhopadhyay, S., Bose, P.K., 2012. Stratigraphic architecture of the Sonia Fluvial interval, India in its Precambrian context. Precambrian Research 214–215, 210–226. Saula, E., Mato, E., Puigdefabregas, C., 2002. Catastrophic debrisflow deposits from an inferred landslide-dam failure, the Eocene Berga Formation, eastern Pyrenees, Spain. In: Baker, V., Martini, I.P., Garzon, G. (Eds.), Floods and Megafloods Processes and Deposits. International Association of Sedimentologists, Oxford, Special Publication 32, pp. 195–209. Schlager, W., 1991. Depositional bias and environmental change-important factors in sequence stratigraphy. Sedimentary Geology 70, 109–130. Schumm, S.A., 1968. River adjustment to altered hydrologic regime-Murrumbidgee River and palaeochannels, Australia. Professional Paper, United States Geological Survey 598, 65. Schumm, S.A., 1969. River metamorphosis. Proceedings of the American Society of Civil Engineers, Journal of the Hydraulics Division HY1, 255–273.

Schumm, S.A., 1972. Fluvial paleochannels. In: Rigby, J.K., Walton, W.K. (Eds.), Recognition of Ancient Sedimentary Environments. Society of Economic Paleontologistsand Mineralogists. Special Publication 16, 98–107. Selley, R.C., 1965. Diagnostic characters of fluviatile sediments of the Torridonian formation (Precambrian) of northwest Scotland. Journal of Sedimentary Research 35, 366–380. Shanmugam, G., 2000. 50 Years of turbidite paradigm (1950–1990s): deep-water processes and facies models – a critical perspective. Marine and Petroleum Geology 17, 285–342. Singh, H., Parkash, B., Gohain, K., 1993. Facies analysis of the Kosi megafan deposits. Sedimentary Geology 85, 87–113. Smith, D.G., 1986. Coarse-grained nonmarine volcaniclastic sediment: terminology and depositional process. Bulletin Geological Society of America 97 (1), 1–10. Sohn, Y.K., Rhee, C.W., Kim, B.C., 1999. Debris flow and hyperconcentrated floodflow deposits in an alluvial fan, northwestern part of the Cretaceous Yongdong Basin, Central Korea. Journal of Geology 107, 111–132. Talbot, M.R., Williams, M.A.J., 1979. Cyclic alluvial fan sedimentation on the flanks of fixed dunes, Janjari, central Niger. Catena 6, 43–62. Todd, S.P., 1989. Stream-driven, high-density gravelly traction carpets: possible deposits in the Trabeg Conglomerate Formation, SW Ireland and some theoretical considerations of their origin. Sedimentology 36, 513–530. Van der Neut, M., Eriksson, P.G., 1999. Palaeohydrological parameters of a Proterozoic braided fluvial system (Wilgerivier Formation, Waterberg Group, South Africa) compared with a Phanerozoic example. In: Smith, N.D., Rogers, J. (Eds.), Proceedings of the 6th International Fluvial Conference. International Association of Sedimentologists Special Publication 28, 381–392. Blackwell, Oxford. Van Weering, T.C.E., Nielsen, T., Kenyon, N.H., Akentieva, K., Kuijpers, A.H., 1998. Large submarine slides on the NE Faeroe continental margin. In: Stoker, M.S., Evans, D., Crampl, A. (Eds.), Geological Processes on Continental Margins: Sedimentation, Mass Wasting and Stability. Geological Society of London Special Publication 129, 5–17. Varadarajan, S., Verma, V.K., 1971. On the nature of contact between Gwalior sill and Kaimur sandstones around Gwalior, Madhya Pradesh. Current Science 40, 404–406. Verma, R.K., Banerjee, P., 1992. Nature of continental crust along the Narmada-Son lineament inferred from gravity and deep seismic sounding data. Tectonophysics 202, 357–397. Walker, R.G., 1984. Shelf and shallow marine sands. In: Walker, R.G. (Ed.), Facies Models, second ed. Geological Association of Canada, Ontario, pp. 141–170. Wells, S.G., Harvey, A.M., 1987. Sedimentologic and geomorphic variation in storm generated alluvial fans, Howgill Fells, northwest England. Geological Society of America Bulletin 98, 182–198. Wendland, C., Fralick, P., Hollings, P., 2012. Diamondiferous, Neoarchean fan-delta deposits, western Superior Province, Canada: sedimentology and provenance. Precambrian Research 196–197, 46–60. Williams, G.P., 1978. Bank-full discharge of rivers. Water Resources Research 14, 1141–1154. Yu, X., Ma, X., Quing, H., 2002. Sedimentology and reservoir characteristics of a Middle Jurassic fluvial system, Datong Basin, northern China. Bulletin Canadian Association of Petroleum Geologist 50 (1), 105–117.

Please cite this article in press as: Chakraborty, P.P., Paul, P. Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India. Journal of Asian Earth Sciences (2013), http://dx.doi.org/10.1016/j.jseaes.2013.09.019